A rocket engine for a spacecraft, such as the space shuttle, burns liquid oxygen and liquid fuel to form a stream of hot, propulsive gases. These fluids are mixed and burned in a combustion chamber to produce energy for propelling the spacecraft. The rocket engine includes a centrifugal pump for supplying liquid oxygen to either an intermediate burner or to the main combustion chamber.
One example of such a centrifugal pump is shown in U.S. Pat. No.: 5,156,534 issued to Burgy, Palgon, and Branstrom. In this example, an impeller forces the liquid into rotary motion. A pump casing extends circumferentially about the impeller and has a volute or manifold housing for receiving flow discharged from the centrifugal impeller. A discharge passage or nozzle is in flow communication with the volute to discharge flow from the pump casing.
The walls of the pressure vessel which form the volute have a plurality of circumferentially extending vanes. The vanes extend between the walls of the pump housing to aid in the collection of the dynamic flow. The vanes aid in turning the flow into static pressure for eventual discharge through the nozzle.
The pump discharges a very high pressure in rocket engines. The leading edge of the radially or circumferentially extending vane, commonly called the "cut-water", is subjected to large tensile forces by reason of the walls being forced apart by the pressure on the interior of the volute or pump housing. As a result, the leading edge must have an acceptable thickness to lower the stress in the leading edge region. The increase in thickness results in bluntness in the leading edge region which decreases pump performance.
The use of radially or circumferentially extending vanes on the interior of the volute and the precise control of the thickness of the vane results in a complex shape on the interior of the pump housing. The pump housing, having this complex shape, lends itself to casting as the preferred method of manufacturing of the pump housing. This places some limitations on the material that is used, particularly in strength and in fatigue life of the structure.
Accordingly, scientists and engineers working under the direction of Applicant's Assignee have sought to develop a stator assembly for a centrifugal pump which reduces tensile stresses in the leading edge of radially or circumferentially extending vanes and need not be entirely of a cast construction.